JPS6331730B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates generally to the field of instruments for spectroscopically measuring and analyzing optical properties of samples. Instruments of this type are currently used in industrial and agricultural applications for colorimetric and quantitative analysis of the components of samples. Furthermore, this type of equipment is also developing applications in the medical field, where samples are spectrally analyzed for diagnostic purposes.

[Conventional technology]

An example of an agricultural application currently in use is equipment that accurately determines the oil, protein, and moisture content in grain or soybeans. Traditional analytical laboratory techniques such as the Kjeldahl method for protein determination are highly accurate, but require the services of a skilled chemist. Moreover, the results are not immediately or quickly useful. Buyers of agricultural products are increasingly interested in accurately and quickly determining the moisture, protein, and oil percentages of the various types of agricultural products they purchase. For example, sales based on guaranteed protein content are widely introduced in wheat export markets. This competitive pressure allows commodity handlers from rural granaries to export terminals to quickly and accurately sort grain and other agricultural products by percentage of protein and, if possible, percentage of fat and moisture. The demand for this is increasing. There has been a significant increase in demand for versatile, yet inexpensive, advanced equipment that combines recent scientific discoveries and improvements in the field of non-destructive testing of agricultural products. In order to be as useful as possible to product handlers, this type of equipment should not require a high degree of skill on the part of the operator, and should not require specialized scientifically based knowledge of the measurement results. Must not be.

Recent developments have provided equipment that can meet some of the above requirements of product handlers. The optical analyzer disclosed by Donald R. Webster in U.S. Pat. We provide automatic testing machines that measure the percentages of various ingredients. The device consists of multiple narrow spectral bandwidth optical filters joined in the form of a rotatable paddle wheel, each filter capable of independently sweeping the incident optical path between the sample and the wide spectral width light source. It is located in As the filter wheel rotates, the spectral bands of light transmitted through each filter shift progressively as the angle of the filter relative to the optical path changes. The shape of the filter wheel has opaque wings extending from the end of each filter to periodically block the passage of light to the sample. Multiple photodetectors are placed to detect the intensity of reflected light from the sample. The output of such a photodetector is
Sampled at predetermined times relative to the rotation of the filter wheel, it provides a value indicative of the intensity of reflected light at a constant wavelength. Electronic circuitry uses this data to calculate three optical density differences corresponding to the water, protein, and oil content of the sample sample. This optical density difference value is automatically substituted into three linear equations, which are solved to provide an indication of the three percentages of oil, water, and protein content of the sample. Each time a new sample is subjected to testing, the instrument described in US Pat. No. 3,861,788 is automatically calibrated with a standard sample, preferably Teflon. The output of the photodetector is
It is amplified by a special circuit that operates by subtracting the current level during periods when the light is cut off from the output when the photodetector is illuminated.

A related but earlier device was published in U.S. Patent No.
No. 3765755 under the name "Optical internal property analyzer"
Eugene R. Ganssle and Donald R. Webster
and is also assigned to the assignee of the present application. In it, a specimen sample is illuminated with light sequentially filtered by a continuously rotating disk with multiple narrow spectral band interference filters. The combined output of several photodetectors placed to receive the light passed through or reflected by the sample is selectively sampled after passing through a logarithmic amplifier to obtain readings at two discrete wavelengths. are obtained, and the readings are then compared with a differential amplifier to obtain the desired measured quantity. US Patent No.
Although the optical system described in No. 3,765,775 is satisfactory for its intended purpose, its ability to measure at various wavelengths is naturally limited by the number of filters the disk has. Therefore, it is not possible to read at a wavelength intermediate between the wavelengths of two adjacent filters. This limitation is alleviated somewhat with the filter wheel construction of the '788 patent.

Other recent prior optical techniques for determining the fat and oil content of meat, for example, include U.S. government-owned U.S. Pat.
No. 3877818 by George F. Button and Karl H.
Disclosed by Norris. The technique, developed at the USDA Agricultural Research Institute in Greenbelt, Maryland, exposes a meat sample to infrared light from an incandescent power source. The infrared rays pass through or are reflected from the meat sample and reach a tilted mirror (a mirror tilted with respect to the optical axis of the optical system);
The light transmitted through the meat by the inclined mirror or the light reflected from the meat is passed through a flat interference filter while changing the angle of incidence. When the tilting mirror is vibrated (reciprocated) to change the angle of incidence on the filter, the wavelength of the radiation passing through the filter changes correspondingly in a narrow spectral band in the infrared region. A photodetector receives the filtered light and generates an electrical signal, which is processed to read out the amount of fat in the sample.

[Problem that the invention seeks to solve]

These and other prior art optical analyzers are limited in the accuracy of their measurements by the specialized optical elements and systems used for spectroscopic analysis. Since various agricultural products require highly accurate content analysis, there is an increasing demand for optical instruments with higher performance to more precisely measure ingredient content.

[Means for solving problems]

The instrument of the invention is designed to be used for both colorimetric and compositional analysis, achieving higher precision in high-speed measurements and detecting darker samples than with prior art high-speed measurement systems. The optical analyzer of the prior art described above is improved by providing a new optical system capable of performing analysis. The instrument of the present invention uses a concave holographic grating that vibrates at high speed to rapidly scan the monochromatic light produced by the grating at varying wavelengths. In concave gratings, the lines of the grating are created using holographic techniques. Concave holographic gratings are available on the market, New Jersey, USA,
It is commercially available from J.-Y Diffraction Grating Company of Methuen. Using a concave grating is preferable to using a planar grating. The reason is that three or more optical elements are required in a plane grating, whereas
This is because, in some cases, it is sufficient to use a single optical element in a concave grating. As a result, alignment at the calibration stage is simplified and the cost of an optical bench with a precise mechanism is reduced. Using concave holographic gratings, it is possible to design optical systems with f-numbers lower than F/1 in some cases, for example. High performance planar grid systems are usually limited to F/4 and above.
The low optical F-number allows a large amount of light energy to pass through the optical system, thereby allowing the present invention to analyze darker samples than is possible with conventional optical analyzers. Furthermore,
Holographic gratings are ghost-free and have lower levels of stray light than grooved gratings. Another advantage of the holographic grating used in the optical system of the present invention is that the extremely high grating density allows for high resolution while maintaining a high energy flux. Another advantage of holographic gratings is that they are corrected for astigmatism and have reduced spherical and coma aberrations.

The holographic grating of the present invention is vibrated at extremely high speeds with a novel cam drive. The cam drive uses two identically shaped conjugate cams to ensure rotation of the grating in both directions. Each cam is shaped so that the grating output changes linearly as the rotational position of the grating changes. The cam is also shaped such that different gratings can be used for different wavelength ranges with the same cam drive.

By using a concave holographic grating, light rays traveling through the entrance slit toward the grating are dispersed into spectral components that are focused on a circumference defined through the entrance slit and the grating. The circumference around which these spectral components are focused is known as the Rowland circle. The exit slit is optimally positioned so that each spectral component dispersed by the grating is best focused and has the least aberrations as the grating oscillates and scans the wavelength range.

Since the holographic grating is vibrated at high speed, by using fast scanning techniques, the present invention allows noise to be removed by averaging over many periods. More specifically, in the optical system of the present invention, the grating oscillates at approximately 300 cycles per minute, which is 10 scans per second when scanning twice per cycle. A dark period is provided at the end of each scan for drift correction (zero point correction). The dark period is provided by a filter wheel having two dark segments spaced 180 degrees apart. The filter wheel is synchronized to the cam drive of the grating so that each dark segment corresponds to the orientation of the grating at one extreme position of the vibration cycle. The output is measured with a photodetector during the dark period to provide the necessary drift correction.

The sample analysis optical device of the present invention uses a polarizer at the entrance slit to polarize the light that passes through the entrance slit and illuminates the grating. The polarizer can be rotated up to 90° so that the polarization axis can be changed.

The present invention further provides a novel technique for modifying the shape and size of the light source to suit the optimum requirements of the optical system. This optical device, which requires a white light source to generate a broad spectral band of light, typically uses an incandescent light bulb, typically containing a tungsten filament. The filament shapes and dimensions of commercially available light bulbs are limited and usually inadequate to meet the optimal requirements of the optical system. Accordingly, in the present invention, the length of the filament is essentially doubled by providing a reflector above or below the actual filament at a position relative to the light source that creates an image of the filament. , so that the entire entrance slit can be completely illuminated by the image of the "elongated" filament light source. In another embodiment of the invention, to approximate a circular light source, the reflector is placed in such a position that the image of the filament is next to the filament itself so as to create a square shaped light source.

By changing the optical system as described above to lengthen the filament, the aspect ratio of the slit optics in the present invention can be optimized. Since a typical value for the height to width ratio of the entrance slit is approximately 5.5, the optical changes described above keep the filament height to width ratio the same.
It is possible to approach a ratio of 5.5, so that the entire slit is completely illuminated by the light of the light source. Other optical modifications that produce a nearly circular light source also provide an ideal light source shape for projecting white light onto the sample.

Both techniques for changing the shape of the light source allow the reflector to be tilted relative to the vertical axis passing through the reflector;
and is achieved by a single structure fabricated such that it can rotate about an axis common to the optical axis of the light source. Accurately adjusting the tilt of the reflector around the vertical axis and the rotational position of the reflector around the optical axis,
The image of the filament can be positioned either to double the effective length of the filament or to square it.

The optical device for sample analysis of the present invention includes an embodiment of an optical lens system that uses a first cylindrical lens at the entrance slit to create an image on the grating at the height of the spherical lens through which the light passes. There is a unique arrangement of. By arranging them in this way, it is possible to ensure that the vertical dimension of the irradiation from the light source on the grating plane corresponds to the height of the grating. Next, a second cylindrical lens is provided at the exit slit in order to focus a virtual image of the width of the exit slit onto the grid. By doing this, the width of the exit slit and the height of the grating that forms the image on the grating are constant regardless of the vibration of the grating, so the shape and size of the grating are constant regardless of the vibration. project a monochromatic light image onto the sample.

Projection of an image of monochromatic light of a constant size is completed by adding a lens to the above embodiment and further providing a variable aperture diaphragm at the point where the real image of monochromatic light is projected. By changing the size of the aperture, the amount and size of the radiation projected onto the sample is controlled.

Embodiments of the invention include a photodetector to detect light transmitted through the sample or reflected from the sample, depending on whichever application is preferred. The present invention also includes a power detection device modified by including an optical fiber that effectively collects light transmitted through or reflected from the sample. The output of the optical fiber is focused onto a photodetector for spectral analysis of the sample.

The sample analysis optical device of the present invention includes other optical devices that use the previously described substantially circular light source to project white light rather than monochromatic light onto the sample. In this example, the sample is placed at the input side of the optical system, and the light reflected from or transmitted through the sample is collected by a number of optical fibers arranged, for example, in a circular manner. The other end of the optical fiber array is arranged in a straight line so that the ends of the optical fibers form an entrance slit. The light is transmitted through the optical fiber by internal reflection so that it completely fills the entrance slit thus created. The optical parameters of this optical fiber array are chosen such that each optical fiber receives a light cone of light reflected from or transmitted through the sample, which is at an angle equal to the acceptance angle of the grating. Therefore, light transmitted by an optical fiber array and emitted from the linearly arranged ends of the optical fibers will be transmitted by the grating by all the light received and transmitted by the optical fiber array. onto the vibrating grid at an angle that completely fills the vertical length of . This improved design allows the light intensity transmitted through or reflected from the sample to be optimally utilized by the grating monochromator. The grating of this example is vibrated at extremely high speeds as described above;
Spectral dispersion of light is performed at the position of the exit slit. The spectral light passing through the exit slit is detected by a photodetector for spectral analysis of the sample.

Other objects and advantages of the invention will be understood by reference to the following detailed description of an embodiment, taken in conjunction with the accompanying drawings.

(Example) In the schematic diagram of FIG. 1, the spacing between certain elements of the optical system is exaggerated for clarity.
As shown in FIG. 1, a tungsten filament light bulb light source 1 emits a broadband spectrum of white light. Light from the tungsten filament is collected by a spherical lens 2 and focused onto an entrance slit 4.
A cylindrical lens 3 provides illumination of a suitable area of the concave holographic grating, indicated by reference numeral 5. Although lens 3 is shown spaced apart from slit 4, it is actually located immediately adjacent to slit 4.

In the optical path between the filter 3a and the cylindrical lens 3,
A polarizer 3b is provided to linearly polarize the light. The polarizer can be rotated 90° around the optical axis, thereby changing the polarization axis. The polarizer allows the sample to be illuminated with polarized light and is useful in compositional analysis applications where the polarization axis is chosen experimentally to most accurately determine the composition of the sample.

The optical system of the novel light source of the present invention is further clarified in FIG. In FIG. 2, the reflector 6 is arranged so that, with respect to the filament 1a of the tungsten filament light source 1, the image 1b of the filament 1a is formed directly above the filament 1a, thereby essentially doubling the length of the tungsten filament. It is placed in a certain position. This optical deformation is important in the optical system of the present application. That is, commercially available tungsten filament lamps do not have a filament with a height-to-width ratio that corresponds to the height-to-width ratio of the input slit like the slit 4 commonly used in monochromator optics. It is from. By essentially doubling the length of the filament 1a by means of the reflector 6, a straight filament light source is obtained which approximately corresponds to the aspect ratio of the entrance slit 4. The spherical lens 2 images the filament and the adjacent filament image in the entrance slit 4, so that the entire area of the entrance slit 4 is completely illuminated. The axis of curvature of the cylindrical lens 3 is horizontal, and this lens serves to focus the vertical dimension of the spherical lens 2 onto the grating 5 so that the vertical dimension of the illumination on the grating surface corresponds to the height of the grating. Infrared filter 3 that removes infrared rays
a is provided to reduce unnecessary heat energy emitted from stray light and stray light sources. Also, if the grating and other elements of the optical system are selected for infrared analysis of the sample, a filter can be used instead of the infrared filter 3a to pass the infrared radiation.

The cross-sectional view in FIG. 3 shows a mechanism for attaching the reflecting mirror 6 to adjust the position of the reflecting mirror 6 so as to form an image of the filament at a desired position. As shown in FIG. 3, the light source 1 is installed in a tube 41, and the lens 2 is installed in the tube 41 so that the center line of the tube 41 and the optical axis are aligned. The lens 2 is actually mounted within a sleeve 43 which can be slid axially within the tube 41 to adjust the axial position of the lens in order to properly adjust the focus of the lens 2. I'm starting to be able to do it. The reflector 6 is mounted on a support member 45, which is pivoted on a hollow, circular support member 47. The support member 45 is pivotably supported on the support member 47 on a shaft 49 located such that the pivot axis is perpendicular to the optical axis of the lens 2 and in line with the center of the surface of the reflector. A set screw 51 is screwed into the rear wall of support member 47 and is spaced from support member 49.
It engages with the back side of 5. A compression spring 53 is located between the back surface of support member 45 and the back wall of support member 47 and engages the back wall of support member 45 on the opposite side of set screw 51 and spaced from shaft 49 . As the set screw 51 advances, the support member 45 pivots, causing the reflector 6 to pivot on the shaft 49 against the pressure of the spring 53. Then, by adjusting the set screw 51, the inclined position of the reflector 6 with respect to the support member 47 is adjusted. The support member 47 forms a cylindrical surface 55 that engages the outer cylindrical surface of the tube 41, and the support member 47 is rotatable relative to the tube 41 about the optical axis of the lens 2. .

In order to use the mechanism shown in FIG. 3 to position the image of the filament in line with itself, as shown in FIG. The tilt position is adjusted with a set screw. By this adjustment, the image 1b of the filament 1a is
a, and as the reflector pivots about axis 49, that distance also changes.
As mirror 6 pivots to space image 1b from filament 1a, rotation of support member 47 about tube 41 rotates image 1b about image 1a. Therefore, by adjusting the tilted position of the reflector 6 with respect to the support member 47 and the rotational position of the support member 47 with respect to the tube 41 and the light source 1 in combination, the filament image 1b can be moved to the position shown in FIG. In position image 1b is aligned with filament 1a and
It is at such a distance that it extends continuously from a. The mechanism illustrated in FIG. 3 is also used for another example of the invention in which the image of the filament is positioned to square the light source. This will be detailed later.

Grating 5 is a concave holographic grating of the type previously described and is vibrated at high speed in both directions as generally indicated by the arrows in FIG. 1 by a cam drive mechanism described below with reference to FIG. The oscillations of the grating 5 are synchronized with the rotation of the filter wheel 7 about its axis, the synchronization ratio being generally indicated in FIG. 1 by the dashed line from the grating 5 to the filter wheel 7.

The holographic grating 5 disperses the white light, which is imaged onto the grating through the input slit 4, into spectral components and focuses it at the position of the output slit 8. Also, when infrared analysis of the sample is intended, a holographic grating that disperses the infrared light is used.

The axis of curvature of the cylindrical lens 9 is vertical, unlike the cylindrical lens 3 whose axis of curvature is horizontal, and the cylindrical lens 9 forms a virtual image on the grating 5 with the width of the exit slit 8. Since the width of the virtual image of the exit slit 8 that created the image on the grating 5 and the height of the grating are constant regardless of the vibration of the grating, the irradiation of a constant size onto the sample by the light dispersed by the grating is as follows. This is effectively achieved even if the grid is vibrating. The vibrations of the grating 5 change the wavelength but do not change the size or shape of the radiation on the sample.

Projecting monochromatic light of constant size is accomplished with the additional lenses and mirrors shown in FIG. 1, including the unique output optics of this embodiment. Since an image having the width of the output slit 8 is formed on the grating 5 by the cylindrical lens 9, an image object having a composite shape of the height of the grating and a virtual image having the width of the output slit is formed at the position of the grating 5. After the light beam passes through the filter wheel 7, the light beam is reflected by a mirror 10 onto a spherical lens 11. The spherical lens 11 forms a real image of the composite of the width of the slit and the height of the grating (the image object) at the position of the aperture 12 having a variable aperture. Since the width of the slit is constant and the height of the grating is constant, this real image created in the aperture 12 is of constant size. If there were no cylindrical lens 9, the width of the image formed in the aperture 12 would change as the grating changes its angle of rotation. By varying the size of the aperture (F-number) of the aperture 12, the amount and magnitude of the illumination from the real image created as described above at the location of the aperture 12 for illuminating the sample 15 is controlled. be done. Irradiation from the image formed at the aperture 12 is then reflected by a mirror 13 onto a spherical lens 14, which is located at the aperture 12.
The image created at the position is copied and focused on the sample 15 placed on the support plate 16. Since the image at the aperture 12 is of a constant size,
The image on the sample is also of constant size. The light diffusely reflected from the sample 15 is then detected by a photodetector 17 for spectral analysis.

FIG. 4 is a diagram illustrating a modification of the embodiment shown in FIG. 1, in which a sample 15 is placed so that monochromatic light passes through the sample. The irradiated light from the aperture 12 is reflected by the mirror 13, passes through the sample 15, and focuses an image on the diffuse white reflector 18 by the spherical lens 14. The radiation transmitted through the sample 15 is reflected by a white reflector 18 and subsequently detected by a photodetector 17 for spectrally analyzing the sample. Alternatively, the sample 15 may be placed close to the variable aperture diaphragm 12 of FIG.
The illumination light that has passed through the aperture 12 and through the sample 15 is subsequently detected by a photodetector 17 .

The filter wheel 7 in FIG. 1 is driven by a motor in synchronization with the vibrations of the grid 5. The filter wheel 7 in FIG. Referring to FIG. 7, a top view of the filter wheel 7 is illustrated. The filter wheel 7 comprises two dark (opaque) segments 7a spaced apart by 180 DEG and two circular sections 7b extending between the two dark segments. Each circular segment is a narrow bandwidth filter, filter wheel 7
Each segment near the top of the filter wheel has a wavelength transmission band that varies linearly to pass longer wavelengths than the segment near the bottom of the filter wheel. The filter wheel 7 is constructed such that one side of the filter is a mirror image of the other side about a straight line passing through the center of the opaque or dark segment 7a.

For each complete oscillation of the grating 5, the filter wheel 7 rotates 360° about its axis and directs the light passing through the exit slit 8 at each corresponding extreme position of the grating during the oscillation cycle of the grating. Each dark segment 7a is positioned and arranged so as to be blocked or occluded. The output of the optical system is measured by a photodetector 17 during these dark periods, and any necessary drift corrections are made. The filter wheel 7 not only limits stray light, but also removes secondary light at half the wavelength of the primary light. For example, if light is transmitted through the exit slit at a wavelength of 800 nanometers, some light must also be transmitted at a wavelength of 400 nanometers. Filter wheel 7 also serves to filter out this light.

5 and 6 show further modifications of the optical systems associated with the samples of FIGS. 1 and 4, respectively.
In FIG. 5, for example, instead of positioning the photodetector 17 to directly receive the light reflected by the sample 15 as in FIG. 1, an optical fiber 20 is provided to receive this reflected light. The reflected light is collected and transmitted to the photodetector 17 by internal reflection. The optical fibers are arranged such that the end face 20a of each fiber bundle is positioned on a conic section so as to collect the illumination light reflected by the sample 15 so as to form a circular distribution toward the sample. Said end face 20
a is attached to a conical support member 55, which is made transparent to reduce the amount of stray light reflected thereby. As shown in Figure 1, mirror 13
reflects the irradiation of the image created at the aperture 12 position,
This image is focused onto the sample 15 by the lens 14. The illumination light reflected by the sample is collected by the optical fiber at its end face 20a and transmitted to the opposite end face 20b of the optical fiber. The end surface 20b is arranged on a plane so as to form a circular shape. The light emitted from end face 20b is then focused by lens 19 onto photodetector 17 for spectrum analysis. The photodetector is substantially smaller than the circle formed by the end face 20b of the optical fiber. The lens 19 focuses all the light emitted from the end surface 20b into a spot on a photodetector whose size corresponds to the size of the photodetector.

FIG. 6 shows a similar modification for the optical detection of radiation passing through the sample 15 already illustrated in FIG. Monochromatic light is focused by lens 14 through sample 15 onto white diffuse reflector 18 . The light reflected by the reflector 18 enters the end face 20a of the optical fiber 20. The optical fibers are disposed on the support member 55 in a conical manner distributed over the circumference, and the reflected light is sent to the opposite end face by the optical fiber 20, and is detected as described in connection with FIG. It is detected by projecting it onto a device. The sample 15 may also be placed in close proximity to the variable aperture aperture 12 of FIG.
The illumination light transmitted through the aperture 12 into the sample 15 is collected by and transmitted through an optical fiber 20 and subsequently detected by a photodetector 17 .

A perspective view of a second embodiment of the invention is shown in FIG. Broad spectral band white illumination from a tungsten filament light source 21 is projected by the optical system shown to form a spot of illumination on a sample 28. The novel light source system is shown more clearly in FIG. 9, in which a tungsten light source 21 with a filament 21a is shown. In this embodiment, since the sample is illuminated with white light rather than the monochromatic illumination used in FIG. 1, the ideal form of illumination projected onto the sample should be a spot or circular light. To achieve this goal, the present embodiment contemplates optically modifying the light source of the tungsten filament, since the tungsten filament is not normally formed in a circular shape. For this purpose, the reflector 22 is positioned so as to form an image 21b of the filament 21a on the side of the filament itself, as shown in FIG. The light source formed in this manner is formed as a square, and a square light source more closely approximates a circular ideal shape than a linear filament. A square filament light source is imaged by lens 24 onto lens 27 . The latter lens 27
further projects an image of the illumination light at the position of the aperture 25 onto the sample. A variable aperture diaphragm 25 is placed in close proximity to lens 24 to control the size, and therefore the dose, of the radiation being projected onto the sample.
Mirror 26 is necessary to bend the light radiation from the light source upwardly towards the sample. Infrared filter 26
a is provided to remove unnecessary thermal energy produced by stray light and stray light sources. Additionally, if the grating and other components of the optical system are selected for infrared analysis of the sample, an infrared filter 2
A filter for passing infrared rays can be used instead of 6a.

The advantage of using two lenses 24 and 27 as described above is that this arrangement creates a substantially round light spot of variable size on the sample. By manipulating the reflector 22 to create an image of the filament next to the filament itself, the shape of the light source is made approximately square, so that the lens 24
The illumination light passing through illuminates substantially the entire lens 24. As a result, when the lens 27 focuses the image of the aperture close to the lens 24 on the sample 28,
An almost uniform circle of light is generated on the sample. The same mechanism illustrated in FIG. 3 is used to position image 21b so that filament 21a and image 21b form a square. Therefore,
A single manufacturing component serves both embodiments in which the sample is illuminated with broadband light and embodiments in which the light is dispersed in a grating and then the sample is illuminated with narrowband light.

The entire input optical system is shown schematically in FIG.
This figure is a longitudinal sectional view of a part of FIG. 8. The circular or spot light projected onto the sample placed on the support plate 34 by the optical system is diffusely reflected by the sample 28. The reflected radiation is collected at the end face of an optical fiber array 29. The optical fiber array 29 consists of a number of individual optical fibers arranged at one end in a conic section to receive reflected radiation from the sample.
The end of the optical fiber is attached to a conical member 55;
The conical member is made transparent to reduce the amount of stray light reflected from the support member. At the other end, the ends of the optical fibers of the optical fiber array 29 are arranged linearly to form an entrance slit 30. The light reflected from the sample 28 is effectively transmitted through the optical fiber by internal reflection, completely filling the entrance slit 30. Optical fiber array 2
The optical parameters of 9 are selected such that each optical fiber receives a light cone of light reflected by the sample 28 (which light cone is at an equal angle to the receiving cone of the grating 31).

Referring again to FIG. 8, the optical fiber array 29
The light transmitted by the optical fiber array and emitted from the linear end face 30 formed by the optical fiber array is
at an angle such that all the light received and transmitted by the optical fiber array 29 completely fills the grating 31;
It is projected onto the grid 31. Optical fiber array 2
9, this improved design allows the intensity of the light reflected by the sample 28 and transmitted through the optical fiber array 29 to be optimally used by the grating 31.

The grating 31 in this embodiment oscillates at high speed as previously described for the embodiment of FIG. 1, providing a rapid scanning of the dispersed spectral light at the location of the exit slit 32. The monochromatic light passing through the exit slit 32 is detected by a photodetector 33 for spectral analysis of the sample. Also, if infrared analysis of the sample is intended, a holographic grating that disperses infrared radiation is used.

A filter wheel 7 of the same construction as the filter wheel 7 of FIG. 7 is placed immediately after the exit slit 32 of FIG. The filter wheel 7 is synchronized with the vibration of the grating 31 for the same purpose as the filter wheel 1 of FIG.

The embodiment of FIG. 8 can be modified to detect light transmitted through the sample, as shown in FIG. Sample 28 is positioned such that a spot of the light source transmitted through sample 28 is reflected by diffuse white reflector 34a. The reflected light is collected by the end face of the optical fiber array 29 and, by internal reflection, returns to the array 29 as described with respect to FIG.
entrance slit 30 through the individual optical fibers of
is transmitted to the opposite end forming a The operation is exactly the same as described for FIG. 8 above.

FIG. 12 schematically shows a cam drive for vibrating the grid 5 of FIG. 1 or the grid 31 of FIG. 7 at very high speeds. The cam drive uses two identical heart-shaped conjugate cams 35, 36 to drive the grid in both directions as shown by the arrows. The shape of the cam is chosen to vary the output of the grating linearly with respect to the angular position of the grating, and also to allow different gratings to be used with the same cam drive for other applications. Each conjugate cam is shown in FIG.
6a, and includes a cam follower (tapepet) associated with each cam. Conjugate cam 35,
36 is driven by a high speed motor 37 via gears 38 and 39. Cam followers 35a, 36
a follows the side of each heart-shaped cam 35, 36 as the cam rotates around the camshaft by means of a pin 40 driven by a motor 37 through gears 38, 39. When the cam follower follows the conjugate cam, the cam follower causes the grating to vibrate very rapidly.

13 and 14 are schematic representations of the extreme positions of the grating and the respective positions of the conjugate cam and its cam followers in a plan view from above of FIG. 12 during the vibration cycle. In FIG. 13, for example, the grid is shown in one extreme position during the vibration cycle, corresponding to the condition in which cam follower 36a is at maximum eccentricity of cam 36, while cam follower 35a is at minimum eccentricity of cam 35. ing. 1st
In Figure 4, the opposite extreme state of the grid is shown, in which an opposite relationship exists for the cams and their cam followers. In FIG. 14, cam follower 35a is at the maximum eccentricity of cam 35, while cam follower 36a is at the minimum eccentricity of cam 36.

In the above cam device, the acceleration and deceleration of the vibrating grid is performed by one of the cam surfaces pressing the cam follower, and both cam followers are kept in engagement with the corresponding cam surface. , does not require a spring. As a result, the cam drive can vibrate the holographic grating at very high speeds, for example 300 cycles per minute, so that the grating can rapidly scan the exit slit 10 times per second. This fast scan allows the present invention to eliminate noise by averaging over a large number of vibration cycles.

In the embodiments of FIGS. 1 and 8, the rotation of the filter wheel 7 is of course synchronized with the cam of FIG. corresponds to Furthermore, as mentioned above, the filter wheel 7 is
Dark segment 7a on one side of filter wheel 7 when the grating and cam drive are in the position shown in FIG.
is placed first so as to block the optical path. The dark segment 7a on the opposite side of the filter wheel 7 similarly blocks the optical path when the grating and cam drive are in the position shown in FIG. The exact manner in which the rotation of the filter wheel is synchronized with the grid vibration is not shown in the drawings, but for example the motor 3 for driving the filter wheel in FIG.
7. Additional gears combined with gears 38, 39 can be easily implemented by a person skilled in the art.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, this specific example is to be considered illustrative and non-limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All modifications within the scope and equivalent interpretation of the claims are intended to be included therein.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an embodiment of the invention using a vibrating hologram grating in which monochromatic radiation reflected from a sample is detected for spectral analysis.
Fig. 2 is a schematic diagram showing the light source device in Fig. 1, Fig. 3 is a sectional view showing a partial installation of the light source device of the optical system, and Fig. 4
The figure is a schematic representation of a variant of FIG. 1 in which the monochromatic radiation transmitted through the sample is detected for spectral analysis. FIG. 5 is an abbreviated version of another variant of FIG. 1, in which the monochromatic light radiation reflected by the sample is collected by a filter device and sent to a photodetector element. 6th
The figure is a schematic diagram similar to FIG. 5 for collecting the radiation transmitted through the sample. FIG. 7 shows a dividing filter used in this optical system. FIG. 8 is a perspective view of a second embodiment of the invention using a vibrating holographic grating in which the white radiation reflected from the sample is focused by a filter and transmitted to a dispersion and detection grating for spectral analysis. . 9 is a schematic illustration of the light source input device of FIG. 8, and FIG. 10 is a schematic illustration of a modification of FIG. 8, in which an optical fiber focuses the radiation transmitted through the sample. FIG. 11 is a schematic plan view of a portion of FIG. 8, showing the light source device and the optical fiber used in the second embodiment. FIG. 12 is a perspective view showing the cam drive structure used in the present invention, and FIG.
FIG. 4 is a schematic diagram of a plan view from above of FIG. 12 showing two different positions of the cam and cam follower during oscillation of the grid. 1...Tungsten filament light source, 2...
Spherical lens, 3... Cylindrical lens, 4... Entrance slit, 5... Grating, 6... Reflector, 7... Filter wheel, 8... Output slit, 9... Cylindrical lens.

Claims (1)

Claims: 1. A concave diffraction grating operable to disperse incident optical radiation into narrow bandwidth components; means for reciprocating said grating; and means for reciprocating said grating; an optical means for projecting; an entrance slit disposed between the optical means and the grating;
an exit slit placed to receive the light radiation dispersed in the grating; a light sensing means for detecting the light radiation passing through the exit slit; and a light sensing means located in the path of the dispersed light radiation at different angular positions thereof. a wheel having at least one light-transmissive segment with a filter that transmits different wavelengths; and means for rotating the wheel in synchronization with the reciprocating movement of the grating, the wheel being light-transmissive; means for rotating the wheel are arranged to position the dark segment so as to block light radiation passing through the exit slit when the grating is in one extreme position; Optical device for sample analysis. 2. An optical apparatus for analyzing a sample according to claim 1, wherein the means for reciprocating the grating comprises a conjugate cam providing drive to the grating by a cam surface in both directions of reciprocation. 3. The optical means includes a filament lamp;
reflector means for producing a real image of said filament lamp alongside and adjacent to the filament of said filament lamp; said filament and said filament adjacent to said filament for illuminating the entire area of said entrance slit; 2. An optical device for analyzing a sample as claimed in claim 1, further comprising means for focusing an image of the object onto said entrance slit. 4. A cylindrical lens positioned on an optical path passing through the exit slit so as to generate a virtual image of the width of the exit slit on the grating, and a virtual image of the width of the exit slit at the position of the grating and a virtual image of the width of the exit slit on the grating. Claims further comprising optical means for focusing a real image of the resultant height from radiation passing through said cylindrical lens and projecting said radiation onto a sample, and light sensing means for detecting radiation from said sample. The optical device for sample analysis according to item 1.